Relay or Ignition switch

[mark48]

My GEHL 5635 won't start below freezing. The glow plug preheat, turn key to left, doesn't stay on (the light illuminates and then switches off). So the question, is it the relay? I've cleaned terminals and connector, no change, or is it the switch? If it's the relay why would it initially close and then open?? It's $200 and before I go that route I'd like to see if anyone else has had similar issue.

 

[foton]

I think what I would do is to use a volt meter on the switch when engaging the heat cycle and see if the voltage is steady or or falls off , I guess you could provide a different power source to the heater wire with it disconnected and see if then it will start after a heat cycle . If you go to the load side of the relay to test use a good size wire as it will pull some extra amps.